A. Field of the Invention
The present invention is broadly related to the field of polyurethane chemistry. More particularly, the invention relates to a process for manufacturing a foamed polymeric material from starting materials which include a bitumen such as an asphalt and a hydroxy fatty oil such as caster oil.
B. Description of the Prior Art
The term "polyurethane foam" is generally applied to foamed polymeric materials in which the polymer contains significant numbers of urethane groups, which have the characteristic structure ##STR1## whether the urethane group repeats regularly throughout the macromolecule or not.
Polyurethane foams are ordinarily prepared by the reaction of a polyisocyanate compound with compounds having two or more "active hydrogens." Such active-hydrogen compounds include polyhydroxy compounds, generally termed polyols, and compounds containing amino groups or carboxyl groups. The active-hydrogen compound can contain functional groups in addition to groups which supply replaceable hydrogens. For example, hydroxyl-terminated polyethers and polyesters have been widely used to prepare polyurethane foams. Castor oil and other hydroxy fatty oils have also been used as active-hydrogen compounds in the production of polyurethane foams, particularly rigid and semi-rigid foams. Suitable catalysts are often included in the reaction mixture in order to speed the polymerization reaction, although the addition of a catalyst is not required in all applications. Gas for producing the foam is usually generated at least in part by adding water to the reactants. The water reacts with the polyisocyanate to produce carbon dioxide for foaming. In addition, blowing agents such as low-boiling halocarbons can be mixed with the reactants to produce gas for foaming. Surfactants and other additives are frequently included in the reaction mixture to regulate the size of the foam cells and otherwise influence the properties of the resulting foam.
Within the polyurethane foam family, it is possible to obtain a wide range of physical and chemical properties of the foam by appropriate selection of the specific raw materials and the reaction conditions. A detailed discussion of prior-art polyurethane compositions may be found in Kirk-Othmer, Encyclopedia of Chemical Technology, 2nd ed., (Interscience, 1970), vol. 21, pp. 56-106.
Attempts have been made to incorporate asphalts and tars into polyurethane compositions by one means or another in order to reduce the costs of the starting materials and to produce a polyurethane material having properties suited for a particular application.
One such attempt is disclosed in U.S. Pat. No. 3,179,610. The '610 patent discloses compositions obtained by blending certain polyurethane-type prepolymers with a bituminous composition such as asphalt or tar. The polyurethane prepolymers are prepared by reacting a molar excess of a polyisocyanate with a compound containing a plurality of hydroxy or carboxy groups which are reactive with isocyanate groups. Castor oil is given as an example of such a compound. By using a molar excess of the polyisocyanate when preparing the polyurethane prepolymer, unreacted isocyanate groups are present for further reaction or curing. The prepolymer thus prepared is blended with a bituminous material at room temperature or an elevated temperature, the weight of the prepolymer being from 5 percent to 25 percent of the total weight of the blend. The resulting blend can be foamed and cured in situ by adding water in amounts to react with the prepolymer, liberating carbon dioxide. The '610 patent discloses using the foamed compositions as a joint filler and sealer. All of the applications for the compositions disclosed in the '610 patent involve bonding the composition to another material in some way.
U.S. Pat. No. 3,810,860 discloses a process for polymerizing crude petroleum hydrocarbons which involves a two-component system. The first component includes a crude petroleum hydrocarbon and an arvlene diisocyanate miscible with the hydrocarbon, and the second component includes a crude petroleum hydrocarbon, a hydrogen donor miscible with the hydrocarbon, and an organic acid miscible with the hydrocarbon. Among the hydrogen donors disclosed in the '860 patent are mixtures of a tertiary amine and castor oil. According to the '860 patent, highly asphaltic crude petroleum hydrocarbons are generally not compatible in the second component, the component which would include castor oil were it to be incorporated in the hydrogen donor.
I have invented a process for manufacturing a foamed polymeric material and products related thereto which possess constellations of useful properties not found heretofore in the art.